This should be Henriette Delphine Rosales who married Baron Élisée de Montagnac.
From Pinterest search; fixed the right corners corners and lower left corner with Photoshop and enlarged by half, increased exposure, and filled in shadows.
Square necklines were almost unheard of for decades, but become stylish in the 70s. The sleeves and waistline are crinoline era holdovers.
Keywords: 1870, Blanchard, Henriette Delphine Rosales, Baronne Élisée de Montagnac, Rosales family, de Montagnac family, Baroness, French, curly coiffure, floral hair ornament, fitted bodice, square neckline, lace bertha, fur, elbow length full sleeves, lace cuffs, shovel waistline. lace-trimmed over-skirt, bustle, under-skirt, bows, fan